ORAU Team

NIOSH Dose Reconstruction Project

Technical Basis Document for the Nevada Test Site 

– Introduction

Document Number:

ORAUT-TKBS-0008-1

Effective Date: 02/04/2004

Revision No.: 00

Controlled Copy No.: ______

Page 1 of 12

Subject Expert: Eugene M. Rollins 

Document Owner

Approval: _Signature on File_____________Date: 02/04/2004

Eugene M. Rollins, TBD Team Leader

Approval: _Signature on File____________ Date: 02/05/2004

Judson L. Kenoyer, Task 3 Manager

Concurrence: _Signature on File_________ Date: 02/06/2004

Richard E. Toohey, Project Director

Approval: __Signature on File___________ Date: 02/06/2004

James W. Neton, OCAS Health Science Administrator

Supersedes:

None

TABLE OF CONTENTS

Section

Record of Issue/Revisions ...................................................................................................................

Page

2

Acronyms ............................................................................................................................................3

1.0 Introduction.................................................................................................................................4

1.1 Purpose.................................................................................................................................4

1.2 Scope....................................................................................................................................4

References ........................................................................................................................................11

Glossary ............................................................................................................................................12
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RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION 

DATE

EFFECTIVE 

DATE

REV. 

NO. DESCRIPTION

Draft 01/05/2004 00-A New Technical Basis Document for the Nevada 

Test Site – Introduction. Initiated by Eugene 

Rollins.

Draft 01/29/2004 00-B Incorporates NIOSH and internal reviewers’ 

comments. Initiated by Eugene Rollins.

02/04/2004 02/04/2004 00 First approved issue. Initiated by Eugene Rollins.
Effective Date: 02/04/2004 Revision No. 00 Document No. ORAUT-TKBS-0008-1 Page 3 of 12

ACRONYMS

DOE U.S. Department of Energy

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000

ft foot

km2 square kilometer

m meter

mi2 square mile

NIOSH National Institute for Occupational Safety and Health

NTS Nevada Test Site

ORAU Oak Ridge Associated Universities

TBD Technical Basis Document

TLD thermoluminescent dosimeter
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1.0

In enacting the Energy Employees Occupational Illness Compensation Program Act of 2000 

(EEOICPA), the U.S. Congress officially recognized the hazardous nature of producing and testing 

nuclear weapons. Under the Act, workers who have developed selected types of cancer (or their 

survivors) may be entitled to compensation and medical benefits. This program is administered by 

the U.S. Department of Labor Office of Worker Compensation. The U.S. Department of Health and 

Human Services National Institute for Occupational Safety and Health (NIOSH) is responsible for 

determining individual worker doses.

INTRODUCTION

The Act requires the estimation of radiological doses from ionizing radiation received by workers in 

the nuclear weapons production programs of the U.S. Department of Energy (DOE) and its 

predecessor agencies (the U.S. Atomic Energy Commission and the Energy Research and 

Development Agency). Methods for implementing provisions of the Act have been promulgated in 

Title 42, Part 82, of the Code of Federal Regulations, “Methods for Radiation Dose Reconstruction 

Under the Energy Employees Occupational Illness Compensation Program Act of 2000”.

1.1 PURPOSE

Oak Ridge Associated Universities (ORAU) leads a Team to support NIOSH in conducting this major 

program. This site profile represents a specific support mechanism to the ORAU Team concerning 

documentation of historical practices at the Nevada Test Site (NTS). Dose reconstructors can use 

this profile to evaluate both internal and external dosimetry data for unmonitored and monitored 

workers and serves as a supplement to, or substitute for, individual monitoring data. This document 

provides a site profile of the NTS that contains technical basis information to be used by the ORAU 

Team to evaluate the total occupational radiation dose for EEOICPA claimants. 

This document provides supporting technical data to evaluate, with claimant-favorable assumptions, 

the total Nevada Test Site (NTS) occupational radiation dose that can reasonably be associated with 

a worker’s radiation exposure. This dose results from exposure to external and internal radiation 

sources from NTS facilities and test operations, to NTS occupationally-required diagnostic X-ray 

examinations, and to onsite environmental releases. The discussions include evaluation of doses that 

could have occurred while the worker was not monitored and other forms of missed dose. Over the 

years, new and more reliable scientific methods and protection measures have been developed. The 

methods needed to account for these changes are identified in this document. 

The doses are evaluated using the NIOSH Interactive RadioEpidemiological Program and the 

Integrated Modules for Bioassay Analysis computer programs. Information on measurement 

uncertainties is an integral component of the NIOSH approach. In addition, this document describes 

the uncertainty evaluation for NTS exposure and dose records.

1.2 SCOPE

The profile comprises six major Technical Basis Documents (TBDs): this Introduction, Site 

Description, Occupational Medical Dose, Occupational Environmental Dose, Occupational Internal 

Dose, and Occupational External Dose. Each TBD has an accompanying attachment that provides 

the critical data for dose reconstruction. 

Site Description

The Site Description (ORAU 2003a) discusses NTS site areas, facilities, operations, and processes.
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The NTS in southern Nevada encompasses approximately 3,500 km2 (1,375 mi2) and was the primary 

location for the testing of nuclear explosives in the continental United States between 1951 and 1992. 

Historic testing above or at ground surface included atmospheric testing in the 1950s and 1960s; 

earth-cratering experiments; and open-air nuclear reactor and rocket testing. Since 1961, testing of 

nuclear explosive devices has occurred mainly in drilled vertical holes or in mined tunnels.

Aboveground nuclear weapons tests began on January 27, 1951, with the detonation of a 1-kiloton 

air-dropped weapon over Frenchman Flat. More than 100 atmospheric tests occurred before the 

signing of the Limited Test Ban Treaty in August 1963. In addition to air drops, atmospheric testing 

included detonations from towers at heights from 30 to 213 m (100 to 700 ft), detonations on the 

surface of the ground, and the use of helium-filled balloons to loft weapons 137 to 457 m (450 to 

1,500 ft) above the ground.

Since 1963, the United States has conducted all of its nuclear weapons tests underground in 

accordance with the terms of the Limited Test Ban Treaty. Therefore, complete containment of all 

nuclear weapons tests was a dominant consideration in nuclear test operations. Various methods 

were used for emplacing nuclear test devices to contain the explosion. The most common method 

was to place a test device at the bottom of a vertical drill hole. Another method was to place a test 

device in a tunnel mined horizontally to a location sufficiently deep to provide containment. There 

were two types of tests in vertical drill holes: lower yield devices in relatively shallow holes in the 

Yucca Flats area (Areas 1 through 10) and higher yield devices in deeper holes on Pahute Mesa 

(Areas 18 through 20). 

Post-test drilling of the cavity formed after a detonation in a vertical drill hole was performed to retrieve 

debris samples. The post-test hole was as small in diameter as possible and was drilled at an angle 

to allow the drill rig to be positioned safely away from the surface at ground zero. It was possible to 

encounter high gas pressures in the cavity because the drillback was often performed within a day or

two of the detonation. 

Reentry and mineback operations related to tests in mined tunnels usually took place within days or 

weeks of a test. These operations took place in a confined underground environment where 

personnel actually entered the test tunnel up to the experiment chambers. There were two exposure 

scenarios during reentry and minebacks. The first scenario was a loss of containment in the drilling or 

coring operation. The second scenario was the possibility of activation products entering the working 

areas of the tunnels by migrating through fissures in the rock. Controlled tunnel purging was an 

intentional release of radioactive material to recover experimental equipment and ventilate test 

tunnels.

Although over 90% of all nuclear weapons tests occurred as predicted, sometimes the unexpected 

occurred. In some cases, the failure resulted in the loss of experimental equipment or required the 

controlled ventilation of a tunnel system to recover equipment. In even more rare cases, the failure 

resulted in the unintentional release of radioactive material to the atmosphere. Ten tests resulted in 

unexpected events. Four of those tests resulted in the detection of radioactivity off the NTS: DES 

MOINES, June 13, 1962; BANEBERRY, December 18, 1970; DIAGONAL LINE, November 24, 1971; 

and RIOLA, September 25, 1980.

Safety tests evaluated the safety of nuclear weapons in accident scenarios. The safety tests used 

mixtures of plutonium and uranium dispersed by conventional explosives. Concurrent with and after 

these detonations, extensive studies were conducted to understand the dispersal and transport of 

these radionuclides in the environment, including uptake by plants and animals.
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A number of activities occurred at the Nuclear Rocket Development Station in Area 25. From 1959 to 

1973, the area was used for a series of open-air nuclear reactor, nuclear engine, and nuclear furnace 

tests and for the High Energy Neutron Reactions Experiment. The goal of the nuclear rocket engine 

test program was to develop an operational nuclear rocket for space travel. Engine exhaust 

dispersed radioactive material at the core and cladding degraded during operation of the engine. 

Shallow borehole tests occurred between 1960 and 1968. Some of these tests were related to safety 

studies; others were part of Project PLOWSHARE to determine if nuclear detonations could be used 

as a method for excavation. The shallow tests resulted in the development of some large ejection 

craters.

The NTS manages radioactive waste. DOE disposes of bulk low-level waste in seven selected Area 3 

subsidence craters that collectively comprise the Area 3 Radioactive Waste Management Site. The 

activity began in the mid-1960s when DOE began removing scrap tower steel, vehicles, and other 

large objects that been subjected to atmospheric testing. From 1979 to 1990, large amounts of 

contaminated soil and other NTS debris were added to the craters. The Area 5 waste management 

site uses pits and trenches for shallow land burial of low-level waste in standardized packaging.

In addition, DOE adopted greater confinement burial (21 to 40 m [70 to 120 ft] deep) for wastes that 

are not appropriate for near-surface disposal due to their radioactive exposure levels. Material was 

disposed from 1984 to 1989. The specific waste types included certain high-specific-activity, low-level 

waste (for example, fuel rod claddings and sealed sources, transuranic waste, and some classified 

material). 

Occupational Medical Dose

The Occupational Medical Dose TBD (ORAU 2003b) describes the technical aspects of dose 

reconstruction from medical X-rays administered before employment and periodically thereafter as a 

condition of employment.

Diagnostic X-ray procedures were a contributor to the occupational radiation exposure of NTS 

workers. In general, the dose from these exposures was not measured or considered or included as 

part of the overall occupational exposure of the employee, although it was clearly related. The 

passage of EEOICPA recognized diagnostic medical X-rays administered in conjunction with routine 

or special physical examinations required for employment as a valid source of occupational exposure.

Unlike occupational exposures incurred during normal work processes, individual diagnostic medical 

X-ray exposures were not monitored, necessitating reconstruction of doses acquired in that manner. 

However, NTS used a unique practice in which employees received film badges on arrival at the 

Mercury gate for work. In some instances, workers wore those badges during initial employment 

physicals, which included routine posterior-anterior and lateral chest X-rays. Examination of these 

badges provided measured doses for those chest X-rays. Based on extensive review of available 

documentation from 1951 to the present, these X-rays were the only two diagnostic medical 

radiographic procedures administered in connection with preemployment or regular postemployment 

medical examinations. Therefore, this analysis evaluated only doses from these two techniques.

A potential problem common to all procedures relates to the conversion of exposure represented by 

entrance skin exposure to absorbed organ dose, and to changes in the definition of dose and the 

creation of numerous dose quantities. Over the 50 or so years since the beginning of NTS 

operations, the quantity known today as exposure has undergone several important conceptual 

changes, as has the application of the unit of exposure and its associated unit, the roentgen. At one 

time, the roentgen was used to quantify the dose from electromagnetic radiation and, when this 
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proved confusing and inexact, was defined as exposure dose to distinguish it from the term absorbed 

dose, which was applicable to any type of radiation. Other dose uncertainties considered include 

measurement error, variation in applied kilovoltage, variation in beam current, variation in exposure 

time, and distance from the worker to the source of the X-rays.

Dose estimates to various organs from chest X-rays have also been calculated for the periods from 

1951 to 1957 and from 1957 to 2000. The calculated dose takes into account the uncertainty 

associated with each of the parameters mentioned above. Tables list the doses received by the 

various organs in the body for convenient reference. 

Occupational Environmental Dose

The Occupational Environmental Dose TBD (ORAU 2004c) applies to both monitored and 

unmonitored workers. The environmental dose is the dose workers receive when working outside the 

buildings or inside the tunnels on the NTS from inhalation of and submersion in radioactive materials 

in the air from onsite releases and resuspension of contaminated soils, direct radiation from plumes, 

and direct exposure to radionuclides incorporated in the soil.

In all, more than 900 nuclear tests have taken place at the NTS as part of the nuclear test program. 

One result of these tests is that the surface soils in many parts of the NTS contain measurable 

amounts of several long-lived radionuclides. Almost all of the aboveground tests contaminated the 

soil near ground zero. Several underground tests vented radioactive material to the surface. A few 

safety tests, in which a nuclear device was destroyed by conventional explosives, scattered plutonium 

(and in some cases uranium) over the nearby ground. In addition, there was fallout of radioactive 

debris from many tests over the northern and eastern parts of the site. This TBD develops methods 

for estimating potential dose from inhalation of resuspended contaminated soils.

Radiation levels at the NTS have been monitored regularly, and safety officials have identified and 

fenced off areas where the soil in heavily contaminated. In many other areas, radionuclide levels are 

not high enough to warrant closing the areas, but they are still above background. This TBD provides 

estimates of average ambient dose for use by dose reconstructors. 

There are several major factors that could affect the accuracy of the average annual intake estimates 

from soil resuspension. The most important factors include the following:

• Uncertainty in and time-dependent nature of the resuspension factor

• Spatial variations in radionuclide soil concentrations

• Duration of exposures

Each of these factors could result in and over- or underestimations of annual intakes of several orders 

of magnitude. 

Atmospheric weapon and safety tests from 1952 to 1963 resulted in the release of radioactive 

materials to the atmosphere. Much of this activity was from relatively short-lived radionuclides that 

decayed in a matter of days or weeks. The volatile radionuclides (such as radioiodines, noble gases, 

and tritium) were diluted in the atmosphere and transported off the site. However, much of the 

nonvolatile, long-lived radionuclides settled back into the soils at various locations. Research is 

currently underway to estimate potential occupational dose that could have been received from these 

volatile radionuclides during the atmospheric testing phase at the NTS.

In the early 1980s, the Environmental Sciences Department recognized that the buildup of radon 

daughter concentrations could pose a potential health problem in tunnels on Rainer Mesa and at other 
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locations at the NTS. In 1984, to determine the concentrations of the radon daughters and the effect 

of environmental conditions on the buildup of these concentrations, scientists conducted radon 

surveys in G-, T-, and N-Tunnels. Section 4 of the NTS TBD discusses the results of these surveys 

as well as surveys conducted in 1991 and 1992. Although measurements were periodically 

performed in the tunnel complexes to ensure adequate worker protection, neither DOE nor its 

predecessor agencies attempted to quantify or record occupational exposure to radon and its 

daughters. Therefore, dose reconstructors should adjust the dose of any employee who was a miner 

or tunnel worker to account for radon. The discussion provides a method for assigning occupational 

radon exposure.

At the present time, processing of radioactive materials at the NTS includes only laboratory analyses. 

Handling of these materials includes only the transport and storage of nuclear explosive devices and 

the operation of radioactive waste management sites for low-level and mixed wastes. Monitoring and 

evaluation of the various activities indicate that the potential source terms of onsite radiation exposure 

are tritiated water vapor from drainage containment ponds for E Tunnel in Area 12; onsite 

radioanalytical laboratories, Area 5 waste management facilities, and other diffuse sources.

Occupational Internal Dose

The Occupational Internal Dose TBD (ORAU 2003d) discusses the internal dosimetry program at the 

NTS. The primary focus was external dosimetry, particularly during atmospheric testing. This 

emphasis was based on animal data showing that the internal dose due to inhalation was small in 

comparison to the external dose. The assumption for atmospheric testing was that external exposure 

was the controlling factor. If the external dose was controlled, the internal dose would be low. Dose 

reconstructions performed for military personnel on the site during atmospheric testing determined 

that this assumption was not valid for individuals in the line of the fallout or in an area where recent or 

previous tests had been performed and resuspension of residual contamination was a possibility.

Each operation at NTS had a different set of radionuclides of concern at the time of the test and 

afterward. Radionuclides were identified for NTS locations, including legacy atmospheric, 

underground, and nuclear reactor/rocket development test areas. Tritium and radioisotopes of cobalt, 

cesium, iodine, uranium, plutonium, and americium are the principal radioisotopes of concern.

Routine bioassays at NTS included quarterly urine samples, annual whole body counts, and new and 

terminated employee whole body counts. At present, a large amount of the radiological work at NTS 

is performed through projects with a specified duration. Routine bioassay monitoring is therefore 

usually part of the project. A baseline sample is collected as necessary, and post-work samples are 

collected at the conclusion of the project. If a project requiring bioassay monitoring is expected to last 

longer than 6 months, bioassay sampling on a quarterly to semi-annual frequency throughout the 

duration of the project is recommended. An exception to this could be a tritium project with high 

exposure potential, for which a relatively high frequency of monitoring is required (e.g., weekly to 

monthly).

The TBD discusses the in vitro minimum detectable activities, the analytical methods and the 

reporting protocols for the radionuclides encountered at the NTS. In addition, the TBD discusses the 

in vivo minimum detectable activities, the analytical methods, and the reporting protocols for the Xand gamma-emitting radionuclides. During atmospheric testing (1951 to 1962), in vivo methods of 

analysis were in place but secondary to other measurements. However, as noted above, the NTS did 

have a bioassay program that included whole body, thyroid, lung, and wound counting. In 1964, the 

Los Alamos National Laboratory identified whole body counting for radionuclides that deliver whole 

body doses. There is no description of where these counts took place; the first reference to onsite 

capability is 1967. It is assumed that the counts occurred at Los Alamos. It is also assumed that the 
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University of California-Berkeley and the Lawrence Livermore National Laboratory performed counts 

at their facilities for their employees that spent time at the NTS. Any records that pertain to REECo 

employees have been retrieved from other locations for inclusion in the REECo (now BN) record 

archives.

The records did not state uncertainties for bioassay measurements. This analysis therefore used 

uncertainties in intake estimates to select the best model and action, which should be taken to reduce 

errors to the extent reasonably achievable and give the most accurate intake estimate practicable.

Occupational External Dose

The Occupational External Dose TBD (ORAU 2003e) discusses radiation monitoring and control 

programs at the NTS: personal dosimetry, area monitoring, source term characterization, and 

measurements of fallout (contamination) dispersion.

During the 1951 to 1958 weapon-testing period, allowable external exposure limits for occupational 

workers at the NTS were generally consistent with the National Council on Radiation Protection and 

Measurements recommendations. After the testing moratorium was ended by the Soviet Union in the 

summer of 1961 and the United States resumed nuclear weapons testing at the NTS, the methods for 

evaluating external doses to workers evolved over the years as new techniques and equipment have 

been developed. Concepts in radiation protection also changed.

The TBD describes dose reconstruction parameters, administrative practices, and dosimeter types 

and technology used for measuring the dose from the types of radiation reported. These parameters 

are discussed for evaluation of doses measured from exposure to beta, gamma, and neutron 

radiation.

For nearly three decades, from the start of operations in January 1951 until 1979, personnel 

dosimeters with photographic emulsions of various types and in various holders (i.e., film badges) 

were used at the NTS. The term film badge, or film badge dosimeter, refers to the entire dosimeter 

issued to personnel, which typically consisted of a dental-sized film packet house in a holder of 

varying sophistication designed to improve the response characteristics of the film itself. Although a 

number of different film types were used for dosimetry at the NTS, they generally had similar 

characteristics and responses to beta and photon radiation. Uncertainties in dosimetry with this film 

are largely, if not exclusively, the result of external factors rather than differences in the films.

Starting in February 1966, thermoluminescent dosimeters (TLDs) were used at the Nuclear Rocket 

Development Station as part of the effluent monitoring program. These dosimeters contained a 

calcium fluoride phosphor bound to a helically wound wire in an evacuated glass tube, and were ideal 

for the purpose intended but unsuitable for personnel dosimetry. On July 1, 1968, a TLD program 

was implemented with the cooperation of the Health Services Laboratory of the Idaho Operations 

Office. The laboratory supplied lithium-fluoride TLD chips and provided experience gained at the 

National Reactor Testing Station. The first routine use of TLDs at the NTS began in 1970. 

With the advent of DOE requirements to restrict personnel exposures to as low as reasonably 

achievable and with emphasis on accurate dosimetry at low doses, the Environmental Sciences 

Department personnel began evaluating TLD systems and neutron dosimeters in the early 1980s to 

replace the then-current film badge and neutron TLD. After evaluating several dosimetry systems, the 

Panasonic 802 TLD and the neutron TLD were determined to be the best combination for the NTS 

exposure conditions. They were put into use in January 1987. 
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The external dosimetry discussion includes sources of bias, workplace radiation field characteristics, 

and the responses of the different beta/gamma and neutron dosimeters in the workplace. An 

evaluation of the original recorded doses based on the established parameters described in the TBD 

should provide the best estimate of dose for individual workers with the least overall uncertainty.
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REFERENCES

ORAU (Oak Ridge Associated Universities), 2003a, Technical Basis Document for the Nevada Test 

Site – Site Description, ORAUT-TKBS-0008-2, Oak Ridge, Tennessee.

ORAU (Oak Ridge Associated Universities), 2003b, Technical Basis Document for the Nevada Test 

Site – Occupational Medical Dose, ORAUT-TKBS-0008-3, Oak Ridge, Tennessee.

ORAU (Oak Ridge Associated Universities), 2003c, Technical Basis Document for the Nevada Test 

Site – Occupational Environmental Dose, ORAUT-TKBS-0008-4, Oak Ridge, Tennessee.

ORAU (Oak Ridge Associated Universities), 2003d, Technical Basis Document for the Nevada Test 

Site – Occupational Internal Dose, ORAUT-TKBS-0008-5, Oak Ridge, Tennessee.

ORAU (Oak Ridge Associated Universities), 2003e, Technical Basis Document for the Nevada Test 

Site – Occupational External Dose, ORAUT-TKBS-0008-6, Oak Ridge, Tennessee.
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GLOSSARY